Effect of pozzolans on the performance of fiber-reinforced mortars

Randomly oriented short fibers have been shown to increase tensile strength and retard crack propagation of cement based materials such as fiber-reinforced mortars for diverse applications, especially in aggressive environments. In the case of reinforced concrete, it is very important to produce a “high quality” cover in order to prevent corrosion of the rebars. In order to obtain a high performance material the use of a pozzolan is advisable because low permeability is achieved. The objective of this research was to determine the effect of pozzolans such as silica fume (SF), fly ash (FA), and metakaolin (MK) on the properties of fiber-reinforced mortars. Different types of natural and synthetic fibers were used. A superplasticizer was used to keep the same workability as that of the control mortar. Results of the mechanical and durability properties of the fiber-reinforced mortars are reported. The results show that a loss of resistance due to embedding fibers in mortar is compensated for by the increase in strength caused by silica fume or metakaolin additions to the mortar. The addition of 15% of SF or MK produces an improvement of up to 20% and 68%, respectively, when compared with those mortars without addition. There is a significant decrease in the coefficient of capillary absorption and chloride penetration when a highly pozzolanic material is incorporated into the matrix. In general, these materials, especially SF and MK, improve the mechanical performance and the durability of fiber-reinforced materials, especially those reinforced with steel, glass or sisal fibers. The fly ash addition had a different performance, which could be attributed to its low degree of pozzolanicity.